In January, a policeman was killed in a similar attack in the town of Swabi.

BBC: Pakistan 'policeman killed' guarding anti-polio worker

On 1 January seven charity workers, six of them women, were shot dead in the Swabi area.

BBC: Pakistan 'policeman killed' guarding anti-polio worker

Seven other charity workers were killed in January in the Swabi area - it is not clear if they were targeted because their charity offered vaccinations or education for girls.

BBC: Polio workers in Pakistan

Our correspondent says that the overwhelming majority of displaced people either live in government buildings or schools, or are being looked after by what are called "host families" in Swabi and Mardan.

BBC: Pakistan displaced 'can go home'

Two ANP workers were killed in a grenade attack in the northwestern district of Swabi, four people died in election violence in the area of Chaman on the Afghan border, and two others were killed in the Mian Channu area of Punjab, Pakistan's state TV said.

WSJ: Irregularities at Polls, Strong Turnout as Pakistan Votes

About 260, 000 people have been living in 21 refugee camps in neighboring Mardan, Swabi, Nowshera, Peshawar and Charssada districts, but the United Nations High Commissioner for Refugees say the "vast majority" of internally displaced Pakistanis have been staying with host families, rented houses or in schools.

CNN: Despair, devastation in war-ravaged Swat Valley

Two ANP workers were killed in a hand grenade attack in the northwestern district of Swabi, four people died in election violence in the area of Chaman on the Afghan border, and two others were killed in the Mian Channu area of Punjab, Pakistan's state TV said.

WSJ: Violence as Pakistan Votes